(Note that all citations refer to the page numbers of
the transcript printed in 10-point Times New Roman, with 6 points interceding
between paragraphs.) As an undergraduate at the University
of Toronto, Al Aho wrote his senior thesis on the minimization of Boolean
functions. He then studied at Princeton with an assistant professor, John
Hopcroft, and a graduate student, Jeff Ullman. For his electrical engineering
general examinations, Aho selected computer science as his major, and communications
theory and mathematics as his minors (1). After completing his thesis,
he observed how Bell Laboratories scientists had co-authored many "key
papers" in the "scientific literature" (3). Moreover, he noted how Hopcroft
had close connections with Bell Labs and how Ullman had joined the Labs.
Finally, he was very impressed with Doug McIlroy, whom he met during a
job interview. So, in 1967, Aho decided to join Bell Labs (3). Like others
in Bell Labs’ math center, he was treated almost as a consultant by other
divisions. He soon realized that he had entered a place where "you were
expected to be [at] the forefront of your field, and be able to interact
with the forefront of your field" (14). He knew that, at Bell Labs, "the
real contributions were the ideas" (14). Once he joined Bell Labs, Aho co-authored
a number of research papers, first with Jeff Ullman, and then with several
other co-workers. He soon stumbled upon what would become the UNIX project,
and found that using the early system "was a much nicer way to write papers
than the old traditional way" (1). Through UNIX, Aho helped develop automata
theory and its applications to programming language parsing and compilation.
He initially worked on grammars that Donald Knuth† had
defined in the mid 1950s (6). Aho fleshed-out portions of the linguist
Noam Chomsky’s hierarchy of grammars that he would eventually apply to
computing (2). In this way, Aho hoped to provide
a theoretical basis for designing and analyzing algorithms, especially
those well-suited for translating high-level programming language source
code into the object code that computers actually run (3). He had noticed
that "the scientific literature, if you could call it that, was very inaccurate....
The proofs did not hold" (6). He wanted to build a "scientific base" on
which one could "iterate and improve" algorithms and techniques, and thereby
construct an "engineering design theory" that would make one's work "unassailable"
(9). Aho recognized the power of formal, mathematical methods, and found
them invaluable for creating pattern-matching algorithms — algorithms that
would prove essential for parsing streams of source code. Also, he acknowledged
his debts to Doug McIlroy, with whom he frequently conversed about "very
unusual words," such as "the longest word in English...that has no repeated
letter" — riddles that formalism ultimately trivialized (7). In any event, Aho and Steve Johnson
eventually used automata theory to automate the construction of parsers
from the mathematical grammars that specify programming languages. Johnson
implemented yacc, which automatically translated
a grammar into a parser of lexical units, and lex,
which automatically grouped characters from a byte stream into lexical
units. Thus, Aho and Johnson essentially automated a task that was once
"considered worthy of a Ph.D. thesis" (4). Using yacc,
Brian Kernighan and Lorinda Cherry generated the troff
preprocessor known as eqn, a package for
typesetting mathematics. Via eqn, Kernighan
and Cherry demonstrated the flexibility and power of formal methods; eqn
successfully realized Kernighan’s "philosophy that language should be like
what a professional uses to communicate, the description of those objects
over a telephone" (4). Aho always prized scientific, formal methods: During
his work with pattern matching, he "was astonished to discover that the
program [based on a deterministic automaton] that I [he] had written ran
several times faster than what this machine language program did [sic]"
(7). Later, Aho and Johnson theorized about
optimizing the output code of automatically generated compilers. Along
with others in the UNIX group, they scientifically tested the speeds of
C programs on different computing machine architectures, and thereby developed
CRISP, a RISC computer optimized for running the stock of C programs in
which Bell Labs had an "enormous investment" (8). Also, Aho noticed how
"newer [programming] languages are much easier to lexically analyze and
to syntactically analyze...the technology has shaped the structure of today's
languages, to some degree" (9). He saw computing as a scientific enterprise
whose testing ground was reality, or, rather, speed, power, and reliability.
In contrast, he viewed the AI community as having made "unsubstantiated
claims" that "can't be justified by scientific experiment" (14). According to Aho, unlike AI, UNIX
contained "a great deal of Darwinism" (10). For example, when Kernighan
and Cherry developed eqn, "they got a rudimentary
form of the language processor to be up and running, and then they let
their friends use it. Then the language evolved on the basis of usage patterns"
(10). According to Aho, the UNIX group realized "very early in the game...that
computing is a worldwide fellowship. Computing is not done in isolation.
We like to have access to other people's ideas, programs, information"
(12). The key is to constantly "refine" one's products by scientific evaluations,
and not to adopt a "dogmatic approach" centered on an "august committee"
such as those some European language designers had formed (10). Aho appreciated
that "there was a great spirit in that UNIX room, in the early days, of
a lot of camaraderie and discussion" (10). In addition to this "spirit," Aho
found byte streams and pipes absolutely essential to the development of
UNIX. Aho saw byte streams as "the common denominator" in UNIX, which had
the quintessential property that "you can compose functions on a byte stream"
(11). Interestingly, even though McIlroy had never published a paper on
such function composition, Aho attributed this idea of pipes to Doug McIlroy,
who "has had these great seminal ideas which not everyone knows about"
(11). Aho cherished "Doug's abilities to comprehend work on a broad front
[even with only ‘cursory’ explanations], and also to appreciate the economy
of expression that theoretical models gave to the work" (11). Moreover,
Aho noted how McIlroy had "a flair for language, a flair for economy of
expression" (3). Aho decided that "UNIX would not be the way it is today
without Doug. And, also, I don't think the work that I would have done
would have had the encouragement..." (11). Thus, as Professor Mahoney remarked,
Doug McIlroy seems to be "the gray eminence" in the history of UNIX (11).

† Knuth is probably the most famous and
influential modern computer scientist. In addition to writing many foundational
articles, he has produced the definitive 3- to 7-volume series, The
Art of Computer Programming.